Metal‐Free Synthesis of Fullerene‐Fused 3,4‐Dihydropyrimido[1,6‐ <i>a</i> ]Indol‐1(2 <i>H</i> )‐Ones via Radical Cyclization

Abstract A series of fullerene‐fused 3,4‐dihydropyrimido[1,6‐ a ]indol‐1(2 H )‐one compounds were synthesized by the N─H/C─H sequential relay radical heteroannulation reaction of [60]fullerene with N ‐alkoxy‐1 H ‐indole‐1‐carboxamides promoted by di‐ tert ‐butyl peroxide (DTBP) and iodine (I 2 ) in the presence of succinimide. This protocol avoids the use of expensive metal salts and shows high regioselectivity, broad substrate scope, and excellent functional group tolerance. A plausible formation mechanism for fullerene‐fused 3,4‐dihydropyrimido[1,6‐ a ]indol‐1(2 H )‐ones is proposed.